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Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Distribution of equivalent stress (in MPa) under maximum displacement (left-hand side) and after unloading (right-hand side) state for the indentation depth of 0.05 mm and friction coefficients: (a) 0, (b) 0.1, (c) 0.2 and (d) 0.3.